1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an induction-type electromagnetic transducer and a method of manufacturing such a thin-film magnetic head.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as a real recording density of hard disk drives has increased. Such thin-film magnetic heads include composite thin-film magnetic heads that have been widely used. A composite head is made of a layered structure including a recording head having an induction-type electromagnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading.
It is required to increase the track density on a magnetic recording medium in order to increase recording density among the performance characteristics of a recording head. To achieve this, it is required to implement a recording head of a narrow track structure wherein the width of top and bottom poles sandwiching the recording gap layer on a side of the air bearing surface (medium facing surface) is reduced down to microns or the order of submicron. Semiconductor process techniques are utilized to implement such a structure.
Reference is now made to FIG. 12A to FIG. 15A and FIG. 12B to FIG. 15B to describe an example of a method of manufacturing a composite thin-film magnetic head as an example of a related-art method of manufacturing a thin-film magnetic head. FIG. 12A to FIG. 15A are cross sections each orthogonal to an air bearing surface of the thin-film magnetic head. FIG. 12B to FIG. 15B are cross sections of a pole portion of the head each parallel to the air bearing surface.
In the manufacturing method, as shown in FIG. 12A and FIG. 12B, an insulating layer 102 made of alumina (Al2O3), for example, having a thickness of about 5 to 10 xcexcm is deposited on a substrate 101 made of aluminum oxide and titanium carbide (Al2O3xe2x80x94TiC), for example. On the insulating layer 102 a bottom shield layer 103 made of a magnetic material is formed for making a reproducing head.
Next, on the bottom shield layer 103, alumina, for example, is deposited to a thickness of 100 to 200 nm through sputtering to form a bottom shield gap film 104 as an insulating layer. On the bottom shield gap film 104 an MR element 105 for reproduction having a thickness of tens of nanometers is formed. Next, a pair of electrode layers 106 are formed on the bottom shield gap film 104. The electrode layers 106 are electrically connected to the MR element 105.
Next, a top shield gap film 107 is formed as an insulating layer on the bottom shield gap film 104 and the MR element 105. The MR element 105 is embedded in the shield gap films 104 and 107.
Next, on the top shield gap film 107, a top-shield-layer-cum-bottom-pole-layer (called a bottom pole layer in the following description) 108 having a thickness of about 3 xcexcm is formed. The bottom pole layer 108 is made of a magnetic material and used for both a reproducing head and a recording head.
Next, as shown in FIG. 13A and FIG. 13B, on the bottom pole layer 108, a recording gap layer 109 made of an insulating film such as an alumina film whose thickness is 0.2 xcexcm is formed. Next, a portion of the recording gap layer 109 is etched to form a contact hole 109a to make a magnetic path. On the recording gap layer 109 in the pole portion, a top pole tip 110 made of a magnetic material and having a thickness of 0.5 to 1.0 xcexcm is formed for the recording head. At the same time, a magnetic layer 119 made of a magnetic material is formed for making the magnetic path in the contact hole 109a for making the magnetic path.
Next, as shown in FIG. 14A and FIG. 14B, the recording gap layer 109 and the bottom pole layer 108 are etched through ion milling, using the top pole tip 110 as a mask. As shown in FIG. 14B, the structure is called a trim structure wherein the sidewalls of the top pole (the top pole tip 110), the recording gap layer 109, and a part of the bottom pole layer 108 are formed vertically in a self-aligned manner.
Next, an insulating layer 111 made of an alumina film, for example, and having a thickness of about 3 xcexcm is formed on the entire surface. The insulating layer 111 is then polished to the surfaces of the top pole tip 110 and the magnetic layer 119 and flattened.
Next, on the flattened insulating layer 111, a first layer 112 of a thin-film coil is made of copper (Cu), for example, for the induction-type recording head. Next, a photoresist layer 113 is formed into a specific shape on the insulating layer 111 and the first layer 112. Heat treatment is then performed at a specific temperature to flatten the surface of the photoresist layer 113. On the photoresist layer 113, a second layer 114 of the thin-film coil is then formed. Next, a photoresist layer 115 is formed into a specific shape on the photoresist layer 113 and the second layer 114. Heat treatment is then performed at a specific temperature to flatten the surface of the photoresist layer 115.
Next, as shown in FIG. 15A and FIG. 15B, a top pole layer 116 is formed for the recording head on the top pole tip 110, the photoresist layers 113 and 115, and the magnetic layer 119. The top pole layer 116 is made of a magnetic material such as Permalloy. Next, an overcoat layer 117 of alumina, for example, is formed to cover the top pole layer 116. Finally, machine processing of the slider including the foregoing layers is performed to form the air bearing surface 118 of the thin-film magnetic head including the recording head and the reproducing head. The thin-film magnetic head is thus completed.
FIG. 16 is a top view of the thin-film magnetic head shown in FIG. 15A and FIG. 15B. The overcoat layer 117 and the other insulating layers and insulating films are omitted in FIG. 16.
In FIG. 15A, xe2x80x98THxe2x80x99 indicates the throat height and xe2x80x98MR-Hxe2x80x99 indicates the MR height. The throat height is the length (height) of portions of the magnetic pole layers facing each other with the recording gap layer in between, between the air-bearing-surface-side end and the other end. The MR height is the length (height) between the air-bearing-surface-side end of the MR element and the other end. In FIG. 15B, xe2x80x98P2Wxe2x80x99 indicates the pole width, that is, the recording track width. In addition to the throat height, the MR height and so on, the apex angle as indicated with xcex8 in FIG. 15A is one of the factors that determine the performance of a thin-film magnetic head. The apex is a hill-like raised portion of the coil covered with the photoresist layers 113 and 115. The apex angle is the angle formed between the top surface of the insulating layer 111 and the straight line drawn through the edges of the pole-side lateral walls of the apex.
In order to improve the performance of the thin-film magnetic head, it is important to precisely form throat height TH, MR height MR-H, apex angle xcex8, and track width P2W as shown in FIG. 15A and FIG. 15B.
To achieve high a real recording density, that is, to fabricate a recording head with a narrow track structure, it has been particularly required that track width P2W fall within the submicron order of 1.0 xcexcm or less. It is therefore required to process the top pole into the submicron order through semiconductor process techniques.
A problem is that it is difficult to form the top pole layer of small dimensions on the apex.
As disclosed in Published Unexamined Japanese Patent Application Heisei 7-262519 (1995), for example, frame plating may be used as a method for fabricating the top pole layer. In this case, a thin electrode film made of Permalloy, for example, is formed by sputtering, for example, to fully cover the apex. Next, a photoresist is applied to the top of the electrode film and patterned through a photolithography process to form a frame to be used for plating. The top pole layer is then formed by plating through the use of the electrode film previously formed as a seed layer.
However, there is a difference in height between the apex and the other part, such as 7 to 10 xcexcm or more. The photoresist whose thickness is 3 to 4 xcexcm is applied to cover the apex. If the photoresist thickness is required to be at least 3 xcexcm over the apex, a photoresist film having a thickness of 8 to 10 xcexcm or more, for example, is formed below the apex since the fluid photoresist goes downward.
To implement a recording track width of the submicron order as described above, it is required to form a resist trench pattern having spacing of the submicron order through the use of a photoresist film. Therefore, it is required to form a fine trench pattern of the submicron order on top of the apex through the use of a photoresist film having a thickness of 8 to 10 xcexcm or more. However, it is extremely difficult to form a photoresist pattern having such a thickness with small spacing, due to restrictions in the manufacturing process.
Furthermore, rays of light used for exposure of photolithography are reflected off the base electrode film as the seed layer. The photoresist is exposed to the reflected rays as well and the photoresist pattern may go out of shape. It is therefore impossible to obtain a sharp and precise photoresist pattern.
In the sloped region of the apex, in particular, rays of light used for exposure that are reflected off the base electrode film include not only rays in the vertical direction but also those in the slanting or horizontal direction reflected off the slope of the apex. The photoresist is thus exposed to those rays of light and the photoresist pattern more greatly goes out of shape.
As disclosed in Published Unexamined Japanese Patent Application Heisei 6-68424 (1994), Published Unexamined Japanese Patent Application Heisei 6-309621 (1994) and Published Unexamined Japanese Patent Application Heisei 6-314413 (1994), for example, a thin-film magnetic head in which the top pole layer is formed on a flat surface has been proposed. Such a head solves the problem found in cases in which the top pole layer is formed on the apex.
The position of an end of the pole portion opposite to the air bearing surface is hereinafter called a zero throat height position. In the thin-film magnetic head disclosed in Published Unexamined Japanese Patent Application Heisei 6-68424 (1994), the zero throat height position is defined by an end of the top pole. In the thin-film magnetic head disclosed in Published Unexamined Japanese Patent Application Heisei 6-309621 (1994), the zero throat height position is defined by an end of the bottom pole. In the thin-film magnetic head disclosed in Published Unexamined Japanese Patent Application Heisei 6-314413 (1994), the zero throat height position is defined by an end of the top pole and an end of the bottom pole. In any of these heads the end that defines the zero throat height position is a surface orthogonal to the recording gap layer. Therefore, in any of these heads the space between the bottom and top pole layers from the air bearing surface to the zero throat height position has a specific length equal to the thickness of the recording gap layer. This space abruptly increases from the zero throat height position toward the side opposite to the air bearing surface.
In such a structure where the space between the bottom and top pole layers abruptly increases near the zero throat height position, however, the flow of magnetic flux passing through the pole layers toward the recording gap layer abruptly changes near the zero throat height position. As a result, the flux saturates near the zero throat height position, and the electromagnetic transducing characteristics of the thin-film magnetic head are reduced. The electromagnetic transducing characteristics are, to be specific, an overwrite property that is a parameter indicating one of characteristics when data is written over a region on a recording medium where data is already written, and a nonlinear transition shift (NLTS) characteristic, for example.
It is an object of the invention to provide a thin-film magnetic head and a method of manufacturing the same for making the pole portions with accuracy and improving the electromagnetic transducing characteristics.
A thin-film magnetic head of the invention comprises: a medium facing surface that faces toward a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. The second magnetic layer includes a throat height defining layer touching a flat surface including the gap layer. The defining layer is formed such that a portion thereof forms a cavity with the recording gap layer, the cavity being located in a position at a specific distance from the medium facing surface. The throat height is defined by an end of the cavity closer to the medium facing surface.
A method of the invention is provided for manufacturing a thin-film magnetic head comprising: a medium facing surface that faces toward a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. The method includes the steps of forming the first magnetic layer; forming the gap layer on the first magnetic layer; forming the second magnetic layer on the gap layer; and forming the thin-film coil. The step of forming the second magnetic layer includes the step of forming a throat height defining layer touching a flat surface including the gap layer. The defining layer is formed such that a portion thereof forms a cavity with the recording gap layer, the cavity being located in a position at a specific distance from the medium facing surface. The throat height is defined by an end of the cavity closer to the medium facing surface.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the throat height is defined by the end of the cavity formed in the portion between the throat height defining layer and the gap layer. The flow of flux passing through the throat height defining layer toward the gap layer smoothly changes near the end of the cavity closer to the medium facing surface, that is, near the zero throat height position.
According to the head or the method of the invention, the interface between the cavity and the throat height defining layer may form a curved surface.
According to the head or the method of the invention, the first magnetic layer may include: a first portion located to face the at least part of the thin-film coil; and a second portion including one of the pole portions and connected to a surface of the first portion facing toward the coil. In addition, the at least part of the coil may be located on a side of the second portion of the first magnetic layer. In this case, an insulating layer may be further provided. The insulating layer covers the at least part of the coil located on the side of the second portion of the first magnetic layer, and has a surface facing toward the gap layer, the surface being flattened together with a surface of the second portion of the first magnetic layer facing toward the gap layer. The end of the cavity closer to the medium facing surface may be located closer to the medium facing surface than an end of the second portion of the first magnetic layer opposite to the medium facing surface.
According to the head or the method of the invention, the throat height defining layer may include a portion for defining a track width.
According to the method of the invention, the step of forming the throat height defining layer may include the steps of forming a seed layer for plating on the gap layer; forming a positive resist layer on the seed layer; forming a frame for making the throat height defining layer by plating on the seed layer and forming a resist remaining portion in a region on the seed layer corresponding to the cavity, by exposing the resist layer through the use of a photomask and developing the resist layer, the photomask including: a light shielding region corresponding to the shape of the frame; a region corresponding to the cavity and located in a position corresponding to the cavity and intercepting at least part of rays of light used for exposure; and a region through which the rays of light pass, the region being located in a region except the light shielding region and the region corresponding to the cavity; forming the throat height defining layer by plating through the use of the frame; and forming the cavity by removing the frame and the resist remaining portion.
Other and further objects, features and advantages of the invention will appear more fully from the following description.